Microsoft says that Windows Phone 8 has been pretty huge for the ecosystem as a whole, because since WP8 was released, app downloads across the platform have more than doubled. Even better news for developers is that paid app revenue has gone up almost 140%. Of course, we always have to keep in mind when seeing this type of comparison that it's important to keep in mind what its being compared against. The Windows Phone 7 ecosystem was obviously weaker than WP8, because Microsoft made it well known that WP7 devices would be left behind. That kind of attitude may have affected the app ecosystem before WP8 was released.
Microsoft announced some other pretty interesting news about the Windows Phone Store. The Store will be expanding developer payout to Afghanistan, Iraq, Montenegro, Serbia, Timor-Leste, and Ukraine, making the total markets supporting developer payout 122. Microsoft has also added 15 new carrier billing partners since August 2012, giving the platform 25 supported partners in 19 markets, which is actually more than is offered through Google Play.
Microsoft obviously has committed to the platform, and is working hard to make it a good ecosystem for developers. Combine that with WP's solid growth numbers, and there's no reason to believe this platform is going anywhere but up.